A computer system is actually comprised of numerous, individual electronic components such as resistors, capacitors and transistors. To combine these electronic components into the thousands of circuit configurations that eventually comprise the entire computer system, the components are either directly "wired" into sheets of resistive material that contain various patterns of conductive materials in them ("circuit boards"); or are contained in integrated chips manufactured from semi-conductive materials, which are generally known simply as "chips". These chips are then usually wired into the circuit boards.
Several circuit boards are connected together by various means to make up the overall computer system. A computer system may be comprised of hundreds of circuit boards, each containing thousands of electronic components and chips all connected together in various circuit configurations.
As computer systems continuously evolve, it is desirable to improve their features, function and capabilities in every respect. For instance, each new generation of computer system is designed with more memory capability, functions faster, performs more functions and is simpler to operate for users than the previous generation.
The method by which these continual computer enhancements are achieved is by adding ever more chips and electronic components and/or replacing old electronic components and chips with new and improved versions. For example, if more memory is needed in a particular computer system, then more memory chips are added; or, if it is desirable that a computer function faster, then the central processing unit (CPU) is replaced with a larger one or an improved one that is comprised of more electronic components and chips.
When a computer system is updated by adding new and larger components or chips to the system, the number of circuit boards that comprise the overall computer system must eventually be increased. The constant addition of electronic components and chips or the replacement of outdated chips with new, larger and improved ones has created configuration problems in present computer systems.
One problem is that there is simply not enough space in the computer system to accommodate all of the additional circuit boards required for the new chips and components. Indeed, space is at a premium in all modern computer systems. Thus, it is desirable to design new computer systems with as many "space saving" features as possible.
One known method of conserving space in a computer system is to concentrate as many chips as possible in a small, enclosed device that is then wired into the circuit board. For example, I.B.M. Corporation manufactures a device that is called a "Thermal Controlled Module", which contains 110 chips ("TCM"). A TCM is comprised of a rectangular-shaped, ceramic substrate populated with approximately 110 chips. A TCM requires at least 2,500 connections to the circuit board accomplished with an array of pins on the bottom of the TCM. A more detailed description of the structure and function of TCM's is provided in IBM Journal of Research & Development 26(1): pp. 30-36, January, 1982, which is incorporated herein by reference.
The design of devices such as the TCM, in which a large concentration of chips is contained, has created other problems. One problem is that these devices require a tremendous amount of power to function. Indeed, supplying the huge amounts of power required by new and updated chips and electronic devices such as the TCM is a problem throughout modern computer systems in general.
Accordingly, large power buses must be used to carry the requisite amount of power from power supplies to the circuit boards in a modern computer system. These large power buses complicate and add to the space problem discussed above, because they consume even more space in the computer system.
Yet another problem with modern computer systems is that the improved components of the system, such as TCM's, require not only huge amounts of power, but power that is supplied at different voltage levels. Thus, even larger power buses are required to supply the power at various levels, again adding to the space problem within the overall computer system.
The shear magnitude of power at different voltage levels required by the components that comprise modern computer systems has also created problems in the design of power buses and the means used to attach them to circuit boards. The usual method for attaching power buses to circuit boards is to solder perpendicular tabs extending from the output end of the bus to pads on the end of the circuit board, so that the bus and circuit board are attached perpendicular to one and other. This method creates several problems when used in a modern computer system.
One problem is inefficiency. Because the power bus is attached to the solder pads instead of directly to the main load contained on the circuit board (possibly a TCM or several TCM's), the power must be transmitted through conductors provided at different levels of the circuit board to the load. Accordingly, power is needlessly lost as it is transmitted through the board conductors to the load. In most instances, this power loss is significant because the power must travel across clearance hole areas manufactured into the conductors. A clearance hole area insulates an electrical connection, such as a signal or different power connection, from the power carried in a particular conductor. These clearance hole areas effectively act as resistors, and thus, power is lost as it travels across them.
Another problem associated with the known method of attaching power buses to circuit boards is that, because the power bus is attached to the board in the same perpendicular plane that the TCM's, input/output devices (I/O's) and other devices are attached to the board, it's mechanical bulk consumes potential component placement sites and restricts their usage.
Yet another problem is that this known method of delivering power to circuit boards often requires more than one power bus; usually four, are required to deliver power to the board. Each of these buses are attached to the front plane of a board assembly with the axis of each bus being perpendicular to the plane of the board to provide the maximum amount of room for components. This orientation, although it reduces the space consumed by the four power buses, still unnecessarily consumes potential component space.
Yet another problem with the known method of attaching power buses to circuit boards is that the bus cannot be easily removed from the circuit board because they are soldered together. Thus, the service and rework times for the board assembly is increased unnecessarily.
Accordingly, it is the object of the present invention to provide a computer system that has a power bus which decreases the space required to accommodate it in the computer system. Another object of this invention is to provide a computer system that has a power bus which provides different levels of voltage to a circuit board with a minimum use of space.
A further object of this invention is to provide a computer system that has a power bus that may be connected directly to a large load, for example a TCM, to minimize or eliminate the space required on a circuit board to connect the bus to the load.
Yet another object of this invention is to provide a computer system that has a power bus that can be quickly attached to and detached from a circuit board to provide easy maintenance of either one.